Landscape properties, habitat dynamics, and the carbon storage potential of seagrass meadows in the Wadden Sea

Vegetated coastal ecosystems of the Wadden Sea, such as salt marshes and seagrass meadows, are important habitats and provide various ecosystem services. Efforts to protect and restore these valuable coastal systems are currently paralleled with an interest to better understand and quantify their carbon sequestration potential. Intertidal seagrass meadows comprise an area of more than 20,000 ha in the Wadden Sea, which might lead to the assumption that significant amounts of carbon are stored in these ecosystems. At present, however, very little data exists on carbon storage and dynamics in seagrass environments in the German Wadden Sea. Seagrasses declined massively about a century ago, but over the last decades underwent a process of unassisted recovery in the Wadden Sea of Schleswig-Holstein (northern Germany). Nevertheless, the two seagrass species, Zostera marina and Zostera noltii, are still mostly absent in similar coastal environments in western Germany and in The Netherlands – providing an example for the potential to enhance both ecosystem quality and carbon storage capacity.

In an ongoing study, we investigate characteristics of the tidal landscapes (e.g., surface elevation and geomorphology, adjacent landscape elements, and anthropogenic structures) and specific habitat properties (biomass productivity, sediment characteristics, hydrodynamic conditions, pore-water nutrients) at seven seagrass sites, located on tidal flats along dike-forelands of the North Sea coast of Schleswig-Holstein, northern Germany.

The aims are to (A) deliver a first assessment of the current carbon stocks, (B) quantify intra-site differences in realized seagrass habitats, and (C) understand differences in parameters that locally drive or inhibit the long-term build-up of carbon in seagrass meadows and their associated sedimentary systems. In this presentation, we will show and discuss our first preliminary results and interpretations.